In recent years, as a standard for a disc type recording medium that is recordable and detachable from a recording and reproducing apparatus, the Blu-ray Disc standard has been proposed. The Blu-ray Disc standard prescribes a disc that has a recording medium having a diameter of 12 cm and a cover layer having a thickness of 0.1 mm. The Blu-ray Disc standard uses as optical systems a bluish-purple laser having a wavelength of 405 nm and an objective lens having a numerical aperture of 0.85. The Blu-ray Disc standard accomplishes a recording capacity of 27 GB (Giga bytes) maximum. As a result, a program of a BS digital high-vision broadcast available in Japan can be recorded for two hours or longer without deterioration of picture quality.
As sources (supply sources) of AV (Audio/Video) signals recorded on the recordable optical disc, an analog signal of for example a conventional analog television broadcast and a digital signal of for example a digital television broadcast such as a BS digital broadcast are expected to be used. The Blu-ray Disc standard has established a sub standard for a method for recording AV signals of such broadcasts.
As a derivative standard of the current Blu-ray Disc standard, there is a movement to develop reproduction-only recording mediums on which movies, music, and the like are pre-recorded. As disc-shaped recording mediums on which movies and music are pre-recorded, DVD (Digital Versatile Disc) has been widely used. The reproduction-only optical disc in accordance with the Blu-ray Disc standard is largely different from and superior to the conventional DVD in a large recording capacity and a high transfer rate that allow high-vision pictures to be recoded for two hours or longer in high quality.
The reproduction-only DVD video standard accomplishes an interactive function with button images and so forth on a menu screen. For example, while a moving picture of the DVD video is being reproduced, a process that calls a menu screen with a remote control commander or the like, selects a button image on the menu screen, and changes the reproduced scene can be performed.
In the case of the DVD video, a menu screen is composed of fixed sub picture data. When the menu screen is called, it is displayed in such a manner that the sub picture data is combined with moving picture data. Button image data is included in the sub picture, data. Patent Document “Japanese Patent Laid-Open Publication No. HEI 10-308924” describes a structure of which sub picture data is combined with moving picture data and the combined data is recorded to a recordable DVD.
However, since the reproduction-only DVD video standard prescribes operations using simple commands, it is difficult to accomplish complicated interactive functions. Thus, the creator needs much labor to accomplish the complicated interactive functions with the reproduction-only DVD video standard.
In addition, the reproduction-only DVD video standard prescribes simple program operations with a region of commands the are executed one after the other. Thus, multi-threaded programming and event-driven programming cannot be performed on the reproduction-only DVD video standard. Although the DVD video standard does not have a function that accesses a network such as the Internet, when the network access function is considered to be accomplished, since response times from the network and the user tend to be long, a multi-threaded process is very effective as a system structure to improve the performance.
In addition, in the DVD video standard, commands are embedded in an AV (Audio/Video) stream of which video data and audio data are multiplexed. As the AV stream is reproduced, the embedded commands are extracted therefrom and executed. In other words, an operation model like tracing a vine is performed. Thus, only when the user selects a button and executes a command corresponding to the button on a title selection menu screen or in a multi-story that contains branches, the next operation is decided. Thus, in the DVD video standard, high speed process techniques that pre-read commands for branch prediction and speculative execution cannot be used.
In addition, from a view point of authoring, which creates discs, the reproduction-only DVD video standard has drawbacks. Now, it is assumed that a button designed to appear at predetermined timing on an AV stream and the timing is moved forward or backward on the time axis. For example, as shown in FIG. 1, buttons designate to appear after button appearance start time t1 to button appearance end time t2 on the AV stream are changed so that the buttons appear after time t3 that is earlier than time t1.
As well known, in the reproduction-only DVD video standard, an AV stream is encoded and packetized as prescribed in the MPEG 2 (Moving Pictures Experts Group 2) standard. Timing management of a reproduction output is performed with pts (Presentation Time Stamp). In the example shown in FIG. 1, the button appearance start time is changed from pts1 corresponding to time t1 to pts3 corresponding to time t3.
In the DVD video standard, navigation information, video data, audio data, and sub picture data are individually packed and multiplexed as one AV stream. Commands and so forth are embedded in the AV stream. Video data, audio data, and sub picture data are designated to appear at their multiplexed times. For example, as shown in FIG. 2A, these data are multiplexed so that predetermined data are reproduced at their predetermined times on the time axis managed at pts intervals.
Since the data are multiplexed in such a manner, when button A designated to appear at time pts1 is changed so that it appears at time pts3, the AV stream shown in FIG. 2A should be re-multiplexed so that sub picture data of button 1 appears at time pts3. When the contents of a command that is executed when a button is selected are changed, the AV stream should be re-multiplexed. When an AV stream is re-multiplexed, it needs to be reproduced by a DVD player and temporarily stored in a memory of the player.
Thus, conventionally, it is difficult to accomplish interactive functions having a higher degree of freedom. To accomplish them, the creator side needs much labor.